JPH0580847B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a receiving device, and in this receiving device, an unnecessary signal having a frequency close to a desired signal is isolated, and is returned to the front stage of the receiving device to substantially eliminate it. However, this allows demodulation of only the desired signal.

One of the advantages of frequency modulated transmission systems is that
This is a "capture" effect. This is the ability of an FM discriminator, such as a phase lock loop or ratio detector, to ``consistently'' demodulate signals whose spectra partially overlap with those of stronger signals, and to ``lock-on'' them. ”. However, this advantage turns into a disadvantage when the desired signal is a weaker signal. The current method of dealing with interference caused by such spectral overlap is to create "guard bands" that exceed the bandwidth needed to transmit information, and to disperse and reduce the power of adjacent frequency transmission channels regionally. It is necessary to make use of the available spectrum in an ineffective manner by making it unnecessary. Even with such costly measures, the problem of interference by stronger signals remains unsolved in fringe areas and in the case of mobile receiving devices.

However, the use of a receiving device that emphasizes selectivity allows a larger number of signal channels to be used in a crowded frequency spectrum than is previously possible.

A superheterodyne radio receiver that detects interference from nearby stations is disclosed in U.S. Pat. No. 4,249,261.
The prior art section of claim 1 of Ogita et al. In this radio receiver, a cancellation signal generated by a phase lock loop following the strongest interfering RF signal is sent to the radio frequency stage of the receiver. The detection device used by Ogita is not frequency dependent (provided that the ratio of the interference to the desired signal strength does not exceed a certain narrow range). , which emits a detection signal indicating that interference from an adjacent channel signal has occurred in the radio receiver; Occurs when a condition lower than another predetermined reference level is detected. The transition of the set of states from one stage to the other is not continuous; the phase lock loop is connected and disconnected from the receiver circuit by a switch according to the criteria mentioned above. Of course, the discontinuous use of phase lock loops usually creates acquisition problems due to the existence of finite acquisition time. The result is either undesirable switch transients or undesired interference occurring simultaneously with the reception of the desired signal.

Many other solutions have been proposed to mitigate or eliminate the capture effect.

For example, in US Pat. No. 3,753,123, Carpenter discloses a technique and apparatus for canceling FM modulated radio waves. Like Ogita, Carpenter also
The cancellation signal is generated from a phase lock loop that follows or attempts to follow the FM signal. Carpenter's invention does not propose a method for distinguishing between two signals using the same modulation method and canceling only the interfering signal; therefore, it is not directly related to the problem targeted by the present invention. does not have.

In U.S. Pat. No. 2,386,528, Wilmotte attempts to selectively discriminate between two FM modulated signals without using frequency discrimination, relying instead on amplitude discrimination.
However, Wilmot's U.S. Patent No. 2,388,200
proposes a solution that is primarily applied to strong FM signals in the presence of relatively weak AM signals.

Harmon U.S. Patent No. 2609535
In this issue, two FMs that have a special relationship with each other
Although a system is disclosed for sending signals on a common channel, this is also not particularly relevant to this application.

Perkins holds U.S. Patent No.
No. 3020403 solves the problem of capture effect by processing the signal obtained by converting a received FM signal into an AM signal so as to favor the weaker of the two signals. I am proposing to solve it.

In US Pat. No. 3,091,735, Moore proposed a method for processing two superimposed signals of different strengths, and stated that it was necessary for the user to make adjustments; A variable gain amplifier is proposed in order to select the signal.

Castellini, U.S. Patent No.
No. 3,092,776 discloses a method and apparatus for reducing interference from radio waves having the same carrier frequency, but this also has no particular relevance to the present application.

Ludwing is a U.S. Patent No.
No. 3205443 proposes an interference signal decomposition system using a tracking attenuator.

Baghdady is a U.S. Patent No.
No. 3,287,645 proposes a circuit for dividing an intermediate frequency signal into two channels. 1st
the channel includes a beat frequency detector, the output of which is connected to one input of the balanced modulator;
The other input of this balanced modulator is an intermediate frequency signal. The second channel includes a double detection device feeding one input of a second balanced modulator, the other input of the second balanced modulator being an intermediate frequency signal. . The output of the second balanced modulator is then passed through a bandpass filter. The output of the bandpass filter and the output of the first balanced modulator are then sent to a summing circuit whose output contains the desired signal and whose amplitude with respect to the unwanted signal is , to such an extent that it is captured by a subsequent FM limiter as well as a detector.

Pagdaday, in U.S. Pat. No. 3,911,366, discloses a technique and apparatus for suppressing reception interference, which includes first and second limiters in a first channel, a limiter in a second channel, and a linear transmission device. , as well as a two-channel output coupler for suppressing disturbances caused by certain difficult forms of disturbance.

Therefore, the main object of the present invention is to eliminate the drawbacks of the prior art and effectively counteract the capture of the demodulator by unwanted signals without losing the advantage of the "capture" effect for receiving the desired signal. The object of the present invention is to provide a receiving device that performs the following functions.

Another object of the invention is to configure communication links with channel assignments, which are mutually exclusive and distributed accordingly within the framework of the state of the art. ,
Signals with the same time modulation are selectively received in adjacent channels.

Yet another object of the invention is to increase the number of mutually exclusive channels, within which signals of the same type of modulation are channeled, while each signal still has the same, Or the previous bandwidth can be allocated. Yet another object of the present invention is to suppress unnecessary signals in a channel adjacent to a selected channel within the same communication link if they interfere with the reception of a desired signal. That's true.

The above object is achieved according to the invention by the receiving device described below. That is, the receiving device according to the present invention includes a receiver having a plurality of connection stages including a front stage and a demodulator, a signal selector, a gain-adjusted feedback device, and a comparator, and the demodulator is A desired signal having a predetermined threshold sensitivity and occupying approximately a predetermined band is input to the receiver, and at least one signal occupying a band that partially overlaps with the predetermined band but is different from the same band. two unwanted signals, said receiver having a receiver terminal operatively located upstream of said demodulator, each signal having a distinctive high frequency spectrum, and a spectrum of said desired signal. and at least a portion of the spectral characteristics of the unwanted signals appear across the receiver terminals, and at least a remaining portion of the unwanted signal still appears at the input of the demodulator, which typically Although demodulation is possible,
requiring at least a predetermined level difference between each of the signals at its input in order to demodulate the desired signal to an acceptable signal-to-noise ratio; the gain-adjusted feedback device having one signal receiving input and connected to the output of the signal selector to select one of the signals appearing at both ends of the signal selector; when the two signals are the unnecessary signals, the receiver terminal section is provided with the spectral characteristics of the unnecessary signals and approximately
Negative feedback is applied to one of the signals that are 180 degrees out of phase, and the signal separator includes a frequency-dependent screening device for screening the unwanted signal to isolate it from other signals. , the unnecessary signal has a measurable output level at the output side of the frequency-dependent sorting device, and the comparator generates an adjustment signal for adjusting the unnecessary signal fed back to the receiver terminal. a receiving device that compares a predetermined level of the unnecessary signal with a reference level, wherein the signal selector successively selects the one of the signals that normally appear at both ends of the receiver terminal section; The adjustment signal is an error adjustment signal that feeds the continuously variable gain adjustment input of the gain adjusted feedback device, the predetermined level is the output level of the frequency dependent discrimination device, and the reference level is a wide and non-continuous variable and configurable over a critical range;
The unnecessary signal still remains at the input end of the demodulator, and the demodulator receives the unnecessary signal at a level lower than the desired signal level due to the error control signal, and the unnecessary signal remains at the input end of the demodulator. The detection of the signal and the path of the controlled level residual unwanted signal to the input of the demodulator is independent of the relative magnitude of the desired signal to the unwanted signal, and is further Due to the excessive strength of the signal received, even when the input upstream of the receiving stage is excessive, the received desired signal has sufficient signal level to reach the threshold sensitivity of the demodulator, thus The receiving device is characterized in that the demodulator is prevented from demodulating the unnecessary signal even though the unnecessary signal at a controlled level remains upstream of the demodulator.

The advantages provided by the present invention are the following facts. That is, the receiving device of the present invention can perform desired,
It can also work over a wide range of unwanted signal levels, can clearly isolate unwanted signals from desired signals, is not forced to operate in situations where there are a lot of unwanted signals, and It operates from the lowest receivable threshold sensitivity to signal levels of excessive strength such that excessive input is applied to the front of the receiver. The present invention does not connect any detection circuit to the circuit, but rather, in a state where signals do not interfere,
The path of the desired signal is such that it prevents the generation of feedback signals.

It will be appreciated that the characteristic spectrum of an unwanted signal does not depend on the frequency of the carrier itself, if the unwanted signal is a carrier modulated by an intelligence carrier frequency. Thus, the spectra characteristic of unwanted signals are e.g.
It can be a radio frequency spectrum or an intermediate frequency spectrum.

Other objects of the invention will become apparent in part from the description of the preferred embodiment, and will also become apparent from the modifications particularly pointed out in the claims. For example, in addition to overcoming various difficulties posed by current spectrum allocation, the present invention provides a method of increasing the number of undesired signals adjacent to selected desired signals by causing a suitably configured receiving device to reject unwanted signals adjacent to selected desired signals. The aim is also to make it possible to significantly improve spectrum utilization.

In FIG. 1, at the input terminal 1 of the receiver, in addition to the desired signal S ₀ there is an interfering and unwanted signal S ₁ . The unnecessary signal _S1 is isolated by the sorting device S,
Its output mS ₁ is the degree of unwanted signal. The output signal mS ₁ of the sorting device S is sent to a gain control amplifier CA. Amplifier CA has a nominal controllable gain g adjusted by its gain adjustment input gr. The phase delay device P is later connected to the gain control amplifier CA which transforms the phase of the output of the gain control amplifier CA.
As a result, the output signal of the phase delay device P is −gmS ₁
=-δS ₁ . Here gm=δ. The output of the phase delay device P is sent to an error adjustment circuit E. As a result, the output signal from the error adjustment circuit is S ₀ + (1-
δ) becomes S ₁ . This signal is sent to a signal selection output circuit W, which substantially generates the desired signal S ₀ at its output. The output circuit W includes a detector whose selectivity threshold is greater than the signal level _S0 .

The gain of the gain-controlled amplifier CA is controlled in a comparator D, which receives at one input the level of the output signal mS ₁ of the screening device S and at the other input a constant reference source R. The difference between both levels mS ₁ and R is the gain control amplifier CA
is sent to the gain adjustment input gr. The reference level R is
It is preset as follows. That is, comparator D
generates a suitable regulation voltage for amplifier CA,
(1-δ)S ₁ is below the threshold of detector W, so that only the desired signal S ₀ is present at its output.

The working principle of the invention can be applied to any device, but is primarily intended for devices suitable for the reception of modulated signals, in particular for the reception of weak frequency modulated signals in fringe areas where there are relatively strong signals that act, for example, as jamming signals. shall be.

The principle of frequency modulation is explained by, for example, McGraw Hill.
It is comprehensively covered in the book ``Frequency Modulation'' by August Hund, Book Company, Inc. Frequency modulation theoretically generates an unspecified number of sidebands, represented by Betzel functions. Unwanted signals from carriers that are adjacent in frequency to the desired carrier to which the receiver is tuned are
It is powerful enough to interfere with the demodulation of unwanted signals. Alternatively, if a portion of the spectrum of the modulated unwanted carrier is in the selected passband for the desired signal and still has sufficient strength, the demodulation circuitry can "capture" all the unwanted signals. can be excluded.

The frequency discriminator type detector of the FM receiver completely rejects weak signals of about 6 db below the desired signal, which are generated by the positional dispersion of frequencies of adjacent carriers and the transmitters transmitting adjacent carriers. Proper distribution of the maximum permissible electric field will alleviate this type of disturbance.

However, different transmit path characteristics and transmit powers for desired and unwanted channels are often associated. As a result, the ratio of desired to unwanted field strength available at the receiver antenna causes intermittent capture of the desired signal by unwanted or interfering signals. That is, both signals are combined without automatic frequency control. This is especially true in the case of mobile receivers, such as car radio receivers. This is because the electric field strength ratio constantly changes and cannot be easily modified by changing the directivity or placement of the antenna.

According to the invention, the unwanted carrier sidebands are fed back with the original radio frequency carrier or shifted down to an intermediate frequency carrier. Thus, each carrier wave, whether that of a desired signal or an unwanted signal, is modulated by a frequency that carries a bundle of information, resulting in a first spectrum comprising the radio frequency carrier and its sidebands. obtain. When the radio frequency carrier is shifted to an intermediate frequency carrier, the first spectrum is shifted to a second spectrum that includes the intermediate frequency carrier and its sidebands. Any unwanted signal in the spectrum is isolated and negatively fed back to an appropriate point or terminal within the receiver, erasing either the original radio frequency (RF) spectrum or the corresponding intermediate frequency (IF) spectrum. In the following description, the principle features of the present invention will be explained in detail using the block diagrams of FIGS. 2 and 8. Both figures show the case where isolation and extinction of unwanted signals occurs at the IF level. Figures 3, 4, 5 and 7 differ only by choosing different locations within the receiver that generate the unwanted signals.

The terms used to describe this invention will be explained below.

S ₀ = desired signal F ₀ = desired carrier frequency S ₁ = adjacent low signal F ₁ = F ₀ −d = adjacent low carrier frequency d = spacing between carriers S ₂ = adjacent high signal F ₂ = F ₀ + d = adjacent high carrier frequency F _i = (reference) intermediate frequency = 10.7Mcs F _L = local oscillator frequency for desired signal = F ₀ + F _i F ₀ ±1/2d = bandwidth required for distortion-free reception f =Modulation (information transmission) frequency It is further taught that whenever a mixer stage receives two frequencies, it produces both a sum and a difference of frequencies at its output. However, generally the sum of frequencies is IF
It can be eliminated since cut-off of the mixer stage can occur successfully following the stage. Therefore, only the frequency difference of adjacent channels that interfere, ie, for example, F _L −F ₁ = (F ₀ +F _i )−(F ₀ −d) = F _i +d and F _L −F ₂ = (F ₀ +F _i )−(F ₀ +d)=F _i −d must be processed.

Next, in FIG. 2, by way of example, two radio frequency stages 10, 12 are connected in series. A variable local oscillator 14 feeds a mixer 16, which local oscillator 14 and mixer 16 include a heterodyne device that shifts the radio frequency spectrum to an intermediate frequency spectrum, and the intermediate frequency stage 20 typically includes:
It passes only the intermediate frequency spectrum of the desired signal and, in a trivial manner, blocks out all other unnecessary ones. An intermediate frequency stage 20 with a nominal bandwidth F _i ±1/2d is connected to a mixer 16 via a summer 18.
is later connected to feed a conventional demodulator stage 22. The demodulated output of demodulator stage 22 is an audio frequency output that is conventionally routed to one or more speakers. Automatic gain control line 2
4 and automatic frequency control lead 26 are connected in a conventional manner.

Adder 18 has the function of outputting the sum of its inputs, but in the absence of adder 18, the circuit elements described above are those of a conventional superheterodyne receiver. The invention applies equally to "straight" receivers. Since the structure of the superheterodyne receiver or the straight receiver is well known, a detailed explanation thereof will be omitted.

Input to the sorting device is obtained from terminal means 28;
This terminal section 28 constitutes the output of the adder 18.
The signal from the terminal section 28 is sent to a second intermediate stage 30. For example, an unwanted signal modulated on an adjacent non-carrier F ₁ =F ₀ -d is characterized by its special spectrum, at least the part of the bandwidth or spectrum allocated to the unwanted signal that is specifically used for frequency modulation. In the case of a broader spectrum, it is passed through the previous RF stages 10, 12 together with the mixer 16. The unwanted signal is sent to one input of adder 18 and is received along with the desired signal by intermediate frequency stage 30. The intermediate frequency stage 30 has a passband set to pass only the intermediate frequency spectrum of unwanted signals.

Furthermore, a level detector 38 is connected to the output of the intermediate frequency detector stage 30, and a comparator 40 is connected subsequently to the level detector 38. The other input of comparator 40 is connected to a reference level source 42.
For example, if reference level source 42 has a DC output, level detector 38 detects the intermediate frequency.
Acts to convert to DC. As a result, comparator 40 provides an adjustment voltage to the gain adjustment terminal of gain adjustment amplifier 32. The input terminals of the gain adjustment amplifier 32 are connected not only directly from the IF stage 30 via leads 31 (switch positions A-B), but also to a PLL connected after the IF stage 30, following isolated unwanted signals.
from the VCO (switch position A'-B', see Figure 6)
It is supplied with isolated and unnecessary signals. The input to gain adjustment amplifier 32 is the VCO output of the phase lock loop connected directly to terminal 28, as will be discussed below in connection with FIG.

The output of the gain adjustment amplifier 32 is connected to a phase delay device 34.
The phase of the signal sent to the adder 18 is shifted by approximately 180° with the phase of the signal being delayed by , and an unnecessary signal is obtained at the other input of the adder 18. Therefore, unnecessary signals at the output and terminal section 28 can be reduced. What is important here is that the amount of negative feedback is controlled by the output of comparator 40. Comparator 40 makes the level of the unwanted signal measured by level detector 38 equal to the value of reference level 42 . The output from the phase delay device 34 is connected directly to the second input of the adder 18 or the output from the second adder 36
is connected to the third input of adder 18 via.
Thereby, another arbitrary input can be obtained from another loop (not shown) including circuit elements similar to the elements 30, 31, 32, and 34. However, the corresponding intermediate frequency stage does not pass through the adjacent high carrier wave F ₂ =F ₀ +d. The passband of the intermediate frequency stage 30 is nominally (F _i −d) ±1/2d, while the passband of the intermediate frequency stages of the other loops is nominally (F _i +
d) ±1/2d.

Referring to FIG. 8, the radio frequency portion of the receiver has been omitted for simplicity, and the same numbers have been used for parts similar to those in FIG. As mentioned above, this disclosure differs from the disclosure shown in FIG.
It is pulled out from the receiver terminal located at the front of the. A bandpass filter 17 is connected downstream of the mixer 16 . This bandpass filter 17 is designed to pass a desired signal, but exclude strong unnecessary signals relatively distant from the desired signal. Designing the bandpass filter 17 in this way is useful in cases where even if the unnecessary signal is far from the desired signal, the strength of the sideband of the unnecessary signal is high and it is close to the desired signal. effective. Adder 18 is adjacent to the rear of mixer 16. The output terminal of the adder 18iv is connected to an intermediate frequency stage 20 for selecting the desired signal, and the output of this intermediate frequency stage is further input to a demodulator 22. Terminal 28iv is connected to the output terminal of adder 18iv. Feedback to unwanted signals adjacent to the desired signal on one side of the spectrum is accomplished by a signal selector, such as a conventional phase lock loop 71. The phase lock loop 71 consists of a phase detector 78, a low pass filter 82, an amplifier 80 and a voltage regulating oscillator (VOC) 83 and is connected after a buffer stage or limiter 77 connected to terminal 28iv. Limituta 77
The output terminal of is connected to one input terminal of phase detector 78. The other input terminal of the phase detector is
Connected to the output terminal of VCO83. This VCO8
3 feeds back the unnecessary signal to the gain adjustment amplifier 32, whose gain is fed back to the comparator 4 as in the other cases.
0 by adjusting the output voltage. One input terminal of comparator 40 is the level of the unwanted signal selected by intermediate frequency stage 30 and is connected after terminal 28iv. This level is detected by a level detector 38 and compared with a preset reference level 42. The output of the gain adjustment amplifier 32 is delayed in phase by 90° by the phase delay circuit 35, and
It is necessary to pass through a suppressor such as a gate 37 before being input to the input terminal.

As in other cases, the reference level 42 is set within a safe range and unwanted signals are reduced to this level by negative feedback. This is intermediate frequency stage 3
Measured after 0 isolation and amplification. Therefore,
By setting the reference level 42 to a large value, it is possible to ensure the operation of the feedback loop. Furthermore, after passing through an intermediate frequency stage 20 designed to select only the desired signals, the remaining unwanted signals will be below the threshold value of the demodulator 22.

Both the desired signal and the unwanted signal are connected to terminal 28.
iv, the phase locking loop 71 locks on the one with higher strength. Therefore, if the desired signal is stronger or only the desired signal is present, unnecessary feedback will occur. In order to avoid this unnecessary feedback, a desired signal and an unnecessary signal are selected by respective intermediate frequency stages 20, 30, and then their levels are compared. Level detector 3
9 is connected after the intermediate frequency stage 20 for selecting the desired signal, and the comparator 41 is connected to the level detector 38,
An output signal is generated based on the output difference of 39. This output signal adjusts a suppression device such as gate 37 by causing summer 18iv to turn off the feedback signal. This is done whenever the desired signal is stronger than the unwanted signal and phase lock loop 71 can be captured by the desired signal.

Referring now to FIGS. 3, 4, 5, and 7, the same parts as in FIGS. 2 and 8 are designated by the same numbers. This embodiment includes the elimination of unwanted signals from the intermediate frequency receiver terminals to the radio frequency receiver terminals and the return of unwanted signals between the radio frequency terminals. As is well known to those skilled in the art, the circuit of this embodiment requires additional heterodyne devices to be connected. This heterodyne device is the fourth,
Mixer 50 in FIGS. 5 and 7 and mixer 46 in FIG. 3 converts the intermediate frequency spectrum of the feedback signal into a radio frequency spectrum. Also, the mixer 48 in FIGS. 4 and 5
is also a heterodyne device, by means of which the radio frequency spectrum of both the desired signal and the unwanted signal is converted into an intermediate frequency spectrum, respectively.

In FIGS. 3 and 4, the oscillation frequencies of these heterodyne devices are oscillated by variable oscillator 14 and have the same frequency. However, the band of intermediate frequency stage 30 is replaced by the band of intermediate frequency stage 20 due to the frequency spacing between the desired signal carrier and the unwanted signal carrier.

5 and 7, intermediate frequency stage 2
0 and 30 are the same, but the oscillation frequency needs to be different from the frequency of the variable oscillator 14 depending on the frequency spacing between carriers. This oscillation frequency is a manually tuned oscillator of 14 ^A (Figure 7).
However, it can also be obtained by a voltage regulating oscillator 54 as shown in FIG.

The voltage regulating oscillator 54 requires an auxiliary circuit as an automatic frequency setting circuit.

Auxiliary circuitry to voltage regulated oscillator (VCO) 54 includes a pulsed voltage generator 62 operable in search mode. This generator is manufactured by McGraw-Hill, John Markus, ``Source Book of Electrical Circuits''.
You can use the one shown in the 1968 edition, chapter 81, page 685ff. The output waveform Wf of the pulse voltage generator 62 serves as an index of the state of use. When energization occurs,
A DC voltage is applied stepwise to the VCO by means of pulses. As the voltage applied to the input of the VCO increases and its oscillation frequency increases, an apple pulse voltage generator is required to search for a band higher than the desired signal, and at the same time search for a lower frequency band than the desired signal. In order to do this, a down-pulse voltage generator is required.

The gate 64 is an actuator that in one state activates the pulse voltage generator 62 and in the other state deactivates the pulse voltage generator 62. When the pulse voltage generator 62 is stopped, the staircase wave becomes flat at that moment.

Clock 66 provides a step signal for pulse voltage generator 62. The output of clock 66 is connected through gate 64 to a pulse voltage generator.

It is sufficient to simply turn off the pulse voltage generator 62 for unnecessary signals. The unnecessary signals here are adjacent carriers F ₁ and F ₂ modulated by the information frequency.
etc. A mixer 68 is used for this purpose. One input terminal of this mixer 68 is VCO
The other input terminals are connected to the output terminal of the variable oscillator 14. mixer 68
The output terminal of is connected to a tank circuit 70 tuned to the frequency d of the spacing between the carriers.
The output of tank circuit 70 is connected to shaping circuit 72 . The output frequency of the mixer 68 is equal to the frequency d (usually
200kcs), the shaping circuit 72 transmits a suppression pulse to the gate 64. A starter such as push button 74 can be manually operated to apply a reset pulse to pulse voltage generator 62 or a start pulse to gate 64. Therefore, providing an output signal to mixer 48
The frequency of the VCO depends on whether the pulse voltage generator 62 is "up" or "down".
F _L ±d is automatically set.

One receiver may be fitted with an up-pulse voltage generator and the other receiver may be fitted with a down-pulse voltage generator so that both adjacent up and down carriers can be removed.

Such a configuration has the following advantages. In other words, the output of VCO 54 is output to mixer 48.
, intermediate frequency stage 30 satisfies the standard intermediate frequency stage set at 10.7 Mcs.

Referring to FIGS. 2-5, "LO" shown in a circle is variable oscillator 14. This is to clarify the connection state between the variable oscillator 14 and the mixer.

If the manually controlled local oscillator 56 shown in FIG. 5a is utilized in place of the voltage controlled oscillator 54, it has the advantage of eliminating the need for an auxiliary frequency setting circuit connected to the oscillator 54.
In such a case, circuit elements 62-74 are not required.

The conductor 31 shown in FIGS. 2 to 5 can be replaced with the circuit elements shown in FIG. 6, and the switch S operates the circuit by switching the circuit from terminals A-B to terminals A'-B'. can be switched from the conductor 31 to the phase lock loop shown in FIG. This applies if each signal has a carrier frequency modulated with an information carrier frequency. A phase lock loop connecting the intermediate frequency stage 30 to the gain setting mechanism removes the desired spectrum and eliminates the interference that has passed through the intermediate frequency stage 30 for feedback and selective attenuation of the interference signal at the receiver terminal mechanism. FM by capturing the signal
There is an advantage in cooperating so that the reception capture capacity is sufficient. The ratio of the desired signal to the interfering signal at the input of the demodulation stage 22 is therefore further effectively increased by the capture effect that occurs during reception of the frequency modulated signal, and of course, for example, if the interfering signal is present in the input circuit of the receiver itself. As long as you don't saturate it, you can get close to infinity.

The phase lock loop shown in FIG.
and an amplifier 80 connected to the phase comparator 78.
low pass filter 82 connected to amplifier 80
and a voltage-controlled oscillator 83 connected to a low-pass filter 82. Oscillator 8
The output of 3 is connected to the other input of phase comparator 78 and to a variable gain signal input or gain adjusted amplifier 32.

FIG. 7 is a block diagram of an example implementation of the invention as an adapter kit or jamming suppression module for use with a standard frequency modulation receiver.

A standard receiver, for example a stereo receiver with two loudspeakers, which is modulated to the desired carrier frequency F ₀ , has a signal input terminal (see antenna input in FIG. 7) and an antenna terminal T. have. The conductors normally connecting terminals I and T are removed and an adapter kit or jamming channel suppression module is connected to terminals T and I.

The generation of the desired signal S ₀ and the unwanted signal S ₂ is similarly illustrated in FIG. 7 using the standard symbols applied to frequency modulated signals and their respective amplitudes. For the sake of clarity,
The symbol is one modulation frequency for each signal.
Used with respect to f ₀ and f ₁ . F ₀ and F ₁ represent the carrier frequency, A ₀ and A ₁ represent the amplitude, and β ₀ and β ₁ represent the modulation index of the desired signal and unwanted signal, respectively.

This invention is not limited to the embodiments described above, and based on the spirit of the invention described above, various changes and modifications can be made to the invention by those skilled in the art without exercising any originality. It should be further understood that it is clear that For example, if the position of one element in a loop can be interchanged with the position of one or more other elements without substantially affecting the function of the loop, no new circuit is formed. That is understood. Furthermore, it should be understood that any variations of the invention described with respect to a receiver may be applied to an adapter kit without departing from the spirit and scope of the invention.

Additionally, it is to be understood that any feature recited in one claim may be combined with other features recited in other claims as appropriate.

[Brief explanation of the drawing]

The drawings show embodiments of the invention, FIG. 1 being a schematic block diagram illustrating the principles of the invention, and FIG. 2 showing a first embodiment of the invention using IF-IF feedback as well as two different FIG. 3 is a schematic block diagram showing a second embodiment of the invention employing IF-RF feedback and two different IF stages; FIG. 4 is a schematic block diagram showing RF-RF feedback. A third embodiment of the present invention employing
A schematic block diagram showing the IF stage, Figure 5, shows the RF-
FIG. 5a is a schematic block diagram showing the use of the manually tunable oscillator of FIG. 5; FIG. 6 is a schematic block diagram of an alternative example of the circuit employed in the embodiments shown in FIGS. 2 to 5, and FIG.
A schematic block diagram of an embodiment using the concept of the invention shown in the figure but comprising a commercially available receiver and an adapter in the form of a jamming channel control module, FIG. FIG. 3 is a schematic block diagram of an alternative example of FIG. 10...first stage, 14, 16, 48, 49, 5
4,56...heterodyne device, 18,20,2
8... Receiver terminal section, 22... Demodulator, 30...
Frequency-dependent sorting device, 32, 35, 37... Feedback device, 41... Comparison device, 62... Pulse voltage generator, 64... Mode operating device, 68... Mixer, 70... Resonant circuit, 71 ...Signal sorter, 7
2... Shaping circuit, 74... Start-up device.

Claims (1)

[Claims] 1. Consists of a receiver having a plurality of connection stages including a pre-stage and a demodulator, a signal selector, a gain-adjusted feedback device, and a comparator, the demodulator having a predetermined The input of the receiver has a threshold sensitivity, and the input of the receiver includes a desired signal occupying approximately a predetermined band and at least one unwanted signal occupying a band that partially overlaps with the predetermined band but is different from the same band. signals are present, the receiver has a receiver terminal operatively located upstream of the demodulator, each signal having a distinctive high frequency spectrum, the spectrum of the desired signal and the At least a portion of the spectral characteristics of the unwanted signal appears across the receiver terminals, and at least a remaining portion of the unwanted signal still appears at the input of the demodulator, which demodulator is typically capable of demodulating each of the signals. wherein at least a predetermined level difference is required between each of the signals at its input in order to demodulate the desired signal to an acceptable signal-to-noise ratio, and the signal selector is connected to the receiver terminal. The gain-adjusted feedback device has one signal receiving input and is connected to the output of the signal selector to select one of the signals appearing at both ends of the receiver terminal. When one of the signals is the unnecessary signal, the one signal of the signals that has the spectral characteristics of the unnecessary signal and is out of phase by approximately 180° is applied to the receiver terminal. and the signal sorter has a frequency-dependent sorting device for sorting out the unnecessary signal to isolate it from other signals, and the unnecessary signal is measured at the output side of the frequency-dependent sorting device. the comparator compares a predetermined level of the unwanted signal with a reference level to generate an adjustment signal for adjusting the unwanted signal fed back to the receiver terminal. The signal selector 7/, 48, 30, 76, 78, 80, 82, 8
3 successively selects said one of said signals normally appearing across said receiver terminal section 28, said adjusted signal being connected to said gain adjusted feedback device 32, 35,
37, the predetermined level is the output level of the frequency dependent discriminator 30, 48, and the reference level is variable over a wide and non-critical range. configurable, so that the unwanted signal still remains at the input of the demodulator 22, and the demodulator 22 eliminates the unwanted signal at a level below the desired signal level by means of the error adjustment signal. The path to the input end of the demodulator 22 for detecting the unwanted signal and controlling the level of the remaining unwanted signal is determined by the relative magnitude of the desired signal with respect to the unwanted signal. is unrelated to
Furthermore, even when the input to the front stage 10 of the receiving stage is excessive due to the excessive strength of the signal received by the receiver, the received desired signal will not reach the threshold sensitivity of the demodulator 22. has a sufficient signal level, thus preventing the demodulator 22 from demodulating the unwanted signal even though the unwanted signal remains at a controlled level upstream of the demodulator 22. A receiving device characterized by: 2. The suppression device 37 is connected to the return device 32, 35, 3
7, the signal selector 71 is capable of selecting a strong signal from among the signals, and the comparator has a comparison device 41 with an output. one of the inputs of the comparator 41 is connected to one output of each stage 20;
The other input is connected to the output of the frequency-dependent sorting device 30, the output of the comparator 41 is connected to the suppression device 37, and when the desired signal is stronger than the respective signals, the feedback device 3
2. The receiving device according to claim 1, wherein another error adjustment signal is provided which functions to suppress the operation of the signals 2, 35, and 37, thereby preventing negative feedback of unnecessary signals. 3. The receiving device according to claim 2, wherein said signal selector 71 has a phase lock loop that captures and locks onto said strong signal. 4. A receiving device according to claim 3, characterized in that said feedback devices (32, 35, 37) include a phase delay device (35) for phase-delaying said one of said signals. 5. The high frequency spectrum of each signal at the input of said receiver is a radio frequency spectrum, and at least one of said stages 10 converts the radio frequency spectrum received at the input into an intermediate frequency spectrum. , the unwanted signal is thereby given a radio frequency spectrum and an intermediate frequency spectrum, and the frequency dependent screening device 48/30,7
6/78/80/82/83 selects the feedback signal to include at least one portion of one of the characteristic spectra. 6 said desired signal is a first radio frequency signal and said first down conversion heterodyne device 14/
16 converts the first radio frequency to a first intermediate frequency and first and second local oscillators 14,
56, each of said stages having a predetermined transfer characteristic for passing said first intermediate frequency therethrough, and said first down conversion heterodyne device 14/ connected to 16,
the unnecessary signal is a second radio frequency signal;
Second downward conversion heterodyne device 49/54,4
8/56 is connected to the receiver terminal 28 for converting the second radio frequency signal into a second intermediate frequency signal, and the frequency dependent screening device 30
is said second downward conversion heterodyne device 48/5
4, 48/56, the local oscillator 14, 56 has a second intermediate frequency stage 30 with a pre-tuned transfer characteristic connected to the pre-tuned transfer characteristic. At least one of the oscillators 14, 56 is a variable oscillator, the first radio signal has a first carrier frequency, and the second radio signal has a first carrier frequency. a second carrier frequency separated from the first carrier frequency by a certain frequency difference;
Automatic frequency setting device 54, 62, 64, 66, 6
6. The receiving apparatus according to claim 5, wherein said oscillators 8, 70, and 72 maintain a frequency difference between said oscillators 14 and 56. 7 The electronic variable oscillator is a voltage adjustable oscillator 5
4, the automatic frequency setting device has a pulse voltage generator 62 that can operate in a search mode when energized, and supplies a DC voltage with an arbitrary number of steps selectable to the voltage adjustable oscillator 54, and operates in a search mode. A device 64 activates or deactivates the search mode of the pulsed voltage generator 62, and the pulsed voltage generator 62 remains at the voltage step produced on its output when receiving the deactivation input from the mode activation device 64; A mixer 68 receives the output of the voltage regulated oscillator 54 upon the presence of one input, receives the output of the other voltage regulated oscillator 14 upon the presence of the other input, and a resonant circuit 70 receives the output of the voltage regulated oscillator 54 upon the presence of the other input. a shaping circuit 7 connected to the output and tuned to the frequency difference between the carrier frequencies;
2 is connected to the output of the resonant circuit 70 and the input of the mode actuator 64 to provide a suppression pulse to the mode actuator 64 as soon as the output frequency of the mixer 68 including the frequency difference is obtained; mode actuator 64 provides the release input to the pulse voltage generator 62 upon receiving the inhibition pulse from the shaping circuit 72 and provides an actuation pulse to the pulse voltage generator 62 upon receiving the start pulse;
7. The receiving device according to claim 6, wherein said voltage-adjustable oscillator 54 electronically follows the frequency of said other voltage-adjustable oscillator 14. 8. A receiver as claimed in claim 7, characterized in that a start-up device (74) provides said start pulse to said mode activation device (64) and a clock (66) provides a step pulse to said pulse voltage generator (62).